Field of the Disclosure
The present disclosure relates to semiconductor devices, and more particularly, to a super-junction structure, a method for manufacturing the super-junction structure and a semiconductor device including the super-junction structure.
Description of the Related Art
High-power semiconductor devices, such as metal-oxide-semiconductor field effect transistors (MOSFETs), insulated gate bipolar transistors (IGBTs) and the like, typically decreases a doping concentration of a drift region for a high breakdown voltage. However, the drift region will have a large on resistance if having a low doping concentration. Thus, the conventional approach cannot take into account both a high breakdown voltage and a low on resistance.
To achieve both a high breakdown voltage and a low resistance in semiconductor devices, a super-junction structure may be used as a drift region, instead of a simple epitaxy layer. The super-junction structure is a structure in which N-type pillar regions and P-type pillar regions are arranged alternatively. FIG. 1 is a structural diagram of a super-junction structure as a drift region of a MOSFET according to the prior art. As shown in FIG. 1, a plurality of P-type pillar regions are formed in an N-type epitaxy layer and are separated from each other. An N-type pillar region is located between two adjacent P-type pillar regions. The P-type region and the N-type pillar regions are arranged alternatively in the epitaxy layer to form a super-junction structure. The super-junction structure achieves both a high breakdown voltage and a low on resistance in the MOSFET.
When a voltage is applied to a substrate of the MOSFET, an avalanche current occurs and flows from a source region to a drain region. The P-type pillar regions are doped uniformly, and the P-type well regions are located at the top surfaces of the P-type pillar regions and have a doping concentration larger than that of the P-type pillar regions. Thus, the avalanche current flows into the P-type well regions at one side and passes through a base resistor RB of a parasitic transistor BJT of the MOSFET. A large voltage drop occurs across the base resistor RB and turns on the parasitic transistor, which in turn amplifies the avalanche current and damage the device. Consequently, the conventional super-junction structure cannot really suppress an avalanche current even in a case that the super-junction structure is used as a drift region of the semiconductor device.